An online measurement system and method for ion energy in a high-power electric thruster

Abstract

The present invention discloses an ion energy measurement system for a high-power electric thruster, including an integrated probe inside a discharge chamber and a data acquisition system outside the discharge chamber; the integrated probe includes a three-probe probe and a metal ring probe; the metal ring probe is an unclosed ring structure wound by metal wire, and the three-probe probe is located inside the metal ring probe, including three metal wires arranged side by side; the data acquisition system obtains the induced potential generated inside the metal ring probe to obtain the current density, and the data acquisition system simultaneously obtains the ion saturation current, positive bias potential and suspension potential of the three-probe probe to obtain the ion density; the ion energy is obtained according to the current density and the ion density. The present invention also discloses an online measurement method for ion energy in a high-power electric thruster. The present invention realizes real-time monitoring of ion energy, can promote the study of energy coupling mechanism of electric thrusters, optimize thruster design, and promote the rapid development of high-power electric thrusters.

Description

Technical Field

[0001] The invention belongs to the field of space electric thrusters and relates to an online measurement system and method for ion energy in a high-power electric thruster. Background Art

[0002] High-power electric propulsion has important application prospects in manned space flight, deep space exploration, space stations and other missions. Compared with other types of space propulsion systems, high-power electric thrusters have the advantages of high thrust density, high specific impulse and long life. It is one of the important development directions for future deep space exploration, long-term space station in orbit, and mobile transfer missions.

[0003] In high-power electric propulsion technology, the working gas must first be ionized to form plasma; then the energy is coupled into the plasma through an electromagnetic field to accelerate the ions; finally, all the ion energy is converted into axial energy and ejected from the nozzle to obtain thrust.

[0004] From the above principle, it can be seen that plasma is an important medium for thrusters to obtain energy and generate thrust, and ion energy is an important parameter in thruster plasma, which directly reflects the thruster energy coupling efficiency. However, high-power electric thrusters generally need to couple energy in a long plasma transport process. In order to carefully study the energy coupling at different stages of plasma transport and improve the thruster structure design, it is necessary to monitor the ion energy parameters of plasma at all times. The existing ion energy measurement method generally uses a multi-grid ion energy analyzer, which has a large measurement system size and a long measurement time, and it is difficult to meet the research and development needs. Summary of the invention

[0005] The purpose of the present invention is to overcome the above defects and provide an ion energy measurement system for a high-power electric thruster, including an integrated probe located inside the discharge cavity of the electric thruster and a data acquisition system located outside the discharge cavity of the electric thruster; the integrated probe includes a three-probe probe and a metal ring probe; the metal ring probe is an unclosed ring structure wound by metal wire, and the three-probe probe is located inside the metal ring probe, including three metal wires arranged side by side; the data acquisition system obtains the induced potential generated inside the metal ring probe, and obtains the current density according to the induced potential, and the data acquisition system simultaneously obtains the ion saturation current, positive bias potential and suspension potential of the three-probe probe, and obtains the ion density according to the ion saturation current, positive bias potential and suspension potential; the data acquisition system obtains the ion energy according to the current density and the ion density. The present invention also proposes an online measurement method for ion energy in a high-power electric thruster based on the above system. The present invention realizes real-time monitoring of ion energy, can promote the study of energy coupling mechanism of high-power electric thrusters, optimize thruster design, and promote the rapid development of high-power electric thrusters.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] An online measurement system for ion energy in a high-power electric thruster includes an integrated probe located inside a discharge cavity of the electric thruster and a data acquisition system located outside the discharge cavity of the electric thruster;

[0008] The integrated probe includes a three-probe probe and a metal ring probe; the metal ring probe is an unclosed ring structure wound by metal wires, and the three-probe probe is located inside the metal ring probe and includes three metal wires arranged side by side;

[0009] The data acquisition system acquires the induced potential generated inside the metal ring probe, and obtains the current density based on the induced potential. The data acquisition system simultaneously acquires the ion saturation current, positive bias potential and suspension potential of the three-probe probe, and obtains the ion density based on the ion saturation current, positive bias potential and suspension potential; the data acquisition system obtains the ion energy based on the current density and ion density.

[0010] Furthermore, among the three metal wires arranged side by side in the three-probe probe, the head of the middle metal wire coincides with the center of the metal ring probe;

[0011] The plane where the metal ring probe is located is perpendicular to the axis of the electric thruster discharge cavity.

[0012] Furthermore, the integrated probe is fixed in the discharge cavity of the electric thruster in a pre-embedded manner;

[0013] The number of integrated probes is ≥3, and the multiple integrated probes are distributed along the axial direction of the electric thruster discharge cavity, and the distribution positions of the multiple integrated probes cover the discharge cavity;

[0014] The three-probe probe is made of tungsten wire with a diameter of 0.3-0.8 mm; the metal ring probe is made of tungsten wire with a diameter of 0.1-0.3 mm.

[0015] Furthermore, the metal ring probe is an open ring structure wound by metal wire, the two ends of the metal wire are the lead-out ends of the metal ring probe, and the tails of the three metal wires arranged side by side of the three-probe probe are the lead-out ends of the three-probe probe; a ceramic tube is provided outside the lead-out end of the metal ring probe and the lead-out end of the three-probe probe, and the lead-out end of the metal ring probe and the lead-out end of the three-probe probe are connected to the data acquisition system after passing through the discharge cavity; the ceramic tube outside the lead-out end of the metal ring probe and the lead-out end of the three-probe probe is sealed with the discharge cavity by sintering.

[0016] Furthermore, among the multiple integrated probes distributed axially in the discharge cavity of the electric thruster, the distance between the last integrated probe and the discharge cavity nozzle is 50 to 80 mm;

[0017] Specifically, multiple integrated probes in the discharge chamber of the electric thruster are evenly arranged along the axial direction of the discharge chamber. This approach ensures the average and universality of data sampling, and ultimately ensures the accuracy of the measurement data. Since the plasma density at the discharge chamber nozzle is low and generally not statistically significant, the ceramic tube in the last integrated probe should be at a certain distance from the sealing position of the discharge chamber and the discharge chamber nozzle to filter out unnecessary data and improve measurement accuracy. According to the size of the discharge chamber and past experience, this distance is generally between 50 and 80 mm.

[0018] Furthermore, it also includes a filtering circuit and a three-probe control system;

[0019] The filter circuit is an LC resonance circuit formed by connecting an inductor and an adjustable capacitor in parallel. The induced potential generated inside the metal ring probe is transmitted to the data acquisition system after passing through the filter circuit. The values ​​of the inductor and the adjustable capacitor of the filter circuit satisfy the following relationship:

[0020] ω 2 =LC;

[0021] Wherein, ω is the loading frequency of the RF power supply of the electric thruster, L is the inductance value, and C is the capacitance value of the adjustable capacitor;

[0022] The three-probe control system is used to power the three-probe probe.

[0023] Furthermore, the data acquisition system includes an acquisition card, an adapter board matching the acquisition card, and a PC;

[0024] The induced potential generated inside the metal ring probe, as well as the electrical signals of the ion saturation current, positive bias potential and suspension potential of the three-probe probe are transmitted to the acquisition card through the adapter board. The acquisition card converts the electrical signals into digital signals and transmits the digital signals to the PC. The PC performs calculations based on the digital signals to obtain current density and ion density, and obtains ion energy based on the current density and ion density.

[0025] Furthermore, the data acquisition system is based on the ion saturation current I s + , positive bias potential V + and the floating potential V f , the ion density is obtained using the following formula:

[0026] T e =(V + -V f ) / ln2

[0027]

[0028] Where α is a constant related to the three-probe probe and plasma; Te is the timing signal of electron temperature; n e is the electron density timing signal, i.e., ion density;

[0029] The ion energy is obtained according to the ion velocity v;

[0030] The ion velocity v is determined by the current density J and the ion density n e , obtained by the following formula:

[0031] J=n e ev

[0032] Here, e is the charge of the electron.

[0033] Furthermore, the data acquisition system obtains real-time evolution parameters of ion energy according to the real-time ion energy obtained, and obtains energy coupling efficiency of the electric thruster according to the real-time evolution parameters of ion energy.

[0034] A method for online measurement of ion energy in a high-power electric thruster is implemented by using the above-mentioned online measurement system for ion energy in a high-power electric thruster, and comprises the following steps:

[0035] The data acquisition system acquires the induced potential generated inside the metal ring probe, and obtains the current density based on the induced potential. The data acquisition system simultaneously acquires the ion saturation current, positive bias potential and suspension potential of the three-probe probe, and obtains the ion density based on the ion saturation current, positive bias potential and suspension potential; the data acquisition system obtains the ion energy based on the current density and ion density.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The three-probe probe is generally used to measure plasma density in the plume region of an electric propulsion system, and can achieve high-speed measurement of plasma density. The present invention uses a three-probe probe and a metal ring probe integrated probe to simultaneously achieve real-time measurement of current density and ion density at the same position, effectively analyze the ion energy at the measurement position, and calculate the real-time evolution law of the ion energy at the measurement point, providing a basis for the optimal design of high-power thrusters;

[0038] (2) The present invention adopts a pre-buried measuring probe, which greatly reduces the interference of the measuring instrument on the plasma, avoids the interference of the radio frequency electromagnetic field on the measuring instrument, realizes the real-time monitoring of the plasma parameters inside the discharge cavity, greatly reduces the volume of the measuring system, and shortens the measurement time. The present invention plays an important role in studying the energy coupling mechanism inside the thruster cavity;

[0039] (3) The integrated probe of the present invention has a simple structure and high reliability, and can be applied to discharge cavities of various types of electric thrusters. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of a preferred online measurement system for ion energy in a high-power electric thruster of the present invention;

[0041] Figure 2 This is a schematic diagram of a preferred integrated probe structure of the present invention;

[0042] In the figure, 1-three-probe probe, 2-metal ring probe, 3-ceramic tube, 4-sintered seal. DETAILED DESCRIPTION

[0043] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0044] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0045] High-power electric thrusters use electromagnetic fields to gradually couple electrical energy into plasma during the plasma transport process and convert it into ion energy. The existing ion energy measurement methods have problems such as large measurement equipment size and long measurement time. In most cases, it is difficult to measure plasma parameters in the discharge cavity of RF thrusters, and real-time monitoring cannot be achieved. It is also impossible to place the measuring instrument in the discharge cavity of the thruster to monitor the energy coupling at different stages of the plasma transport process, which has caused great difficulties in studying the energy coupling mechanism in high-power electric thrusters.

[0046] The present invention aims at the efficient energy coupling of a high-power electric thruster with a power of 50kW, and proposes a real-time measurement scheme for ion energy in a high-power electric thruster. A plurality of integrated probes are embedded in the high-power electric thruster, and the three-probe system and the current density measurement system are integrated to efficiently and real-timely measure the ion density n at different positions. e And current density J, according to the formula J = n e ev(where n e Represents ion density, e represents electron charge), calculates the ion velocity v, and thus obtains the ion energy. The measured data is processed through integral calculation to obtain the real-time evolution parameters of ion energy, so as to analyze the energy coupling efficiency of the high-power electric propulsion system, and analyzes the acceleration effect and acceleration mechanism of the thruster on ions.

[0047] Embodiment 1:

[0048] like Figure 1, this embodiment is a high-power electric thruster ion energy measurement system, including an integrated probe, a three-probe control system, a filtering circuit, a transmission cable and a signal differential amplification data acquisition system.

[0049] The integrated probe includes a three-probe probe and a metal ring probe, which can simultaneously extract ion density and current density to obtain ion energy, greatly simplifying the structure of ion energy data acquisition and shortening the measurement time, so that the integrated probe can be placed inside the thruster discharge cavity for real-time measurement; Figure 2 As shown in the figure, 1 represents a three-probe probe, 2 represents a metal ring probe, 3 represents a ceramic tube, and 4 represents a sintered seal. Specifically, the three-probe probe is composed of three tungsten wires with a diameter of 0.5 mm. The tip of the tungsten wire is exposed at 5 mm and is used to collect plasma parameters. The three tungsten wires are 1 mm apart and arranged side by side. The other positions of the tungsten wires, that is, the tails of the tungsten wires are protected by a 5 mm long ceramic tube. The ceramic tube is sintered and sealed with the discharge cavity and led out of the discharge cavity, leaving a terminal connected to the power control system. The power control system is the same as the existing three-probe control system; the metal ring probe is wound with a tungsten wire with a diameter of 0.2 mm, and the diameter of the ring is 10 mm. It is placed outside the three probes to ensure that the three probes are in the same measurement position as the ring. The two interfaces of the ring, that is, the two lead-out ends of the tungsten wire are protected by ceramic tubes, which are also led out of the discharge cavity. The junction between the ceramic tube and the discharge cavity is sintered and sealed with the discharge cavity. Outside the discharge cavity, the three-probe probe lead-out end is directly connected to the data acquisition system, the metal ring probe is connected to the filter circuit, and then input into the signal differential data acquisition system through the transmission line.

[0050] 4 to 5 integrated probes are pre-buried inside the discharge cavity. The spacing between the integrated probes is adjusted according to the length of the discharge cavity so that it can cover the entire discharge cavity (the length of the discharge cavity of different types of electric thrusters varies) to monitor the plasma transport process. The sealing position of the last integrated probe is 60mm away from the nozzle, and the spacing between the sealing positions of every two integrated probes is 80mm.

[0051] The data acquisition system consists of a PC equipped with an acquisition card and an adapter board that matches the acquisition card. It is responsible for collecting the original signals of the integrated probe, including the induced potential generated inside the metal ring probe and the ion saturation current, positive bias potential and suspension potential of the three-probe probe. In the three-probe probe, two of the three probes form a double probe to measure the ion saturation current I s + and the positive bias potential V + , the last probe is used to measure the floating potential V fAfter the integrated probe collects the corresponding signal, the signal is transmitted to the acquisition card through the adapter board. The acquisition card converts the collected electrical signal into a digital signal and transmits it to the PC. Finally, the PC calculates the ion density and current density through some algorithms. The core principle of the ion density algorithm is as follows:

[0052] T e =(V + -V f ) / ln2

[0053]

[0054] Among them, α is a constant related to the probe and the discharge material. Therefore, it is easy to obtain the timing signal T of the electron temperature from the original signal. e , and then the electron density time series signal n can be calculated through the electron temperature time series signal e , that is, the ion density.

[0055] The filter circuit is an LC resonant circuit, which connects the inductor and the adjustable capacitor in parallel, and adjusts the capacitance of the capacitor according to the operating frequency of the electric thruster RF power supply to satisfy the relationship ω 2 =LC. Where ω is the loading frequency of the RF power supply of the electric thruster, L is the circuit inductance, and C is the circuit capacitance.

[0056] One end of the filter circuit is welded to the metal ring probe joint outside the discharge cavity, and the other end is welded to the transmission line. The transmission line is a radio frequency transmission line with a characteristic impedance of 50Ω. After the transmission line is connected to the filter circuit, the other end is fed into the signal differential amplification data acquisition system.

[0057] In summary, the online measurement system of the present invention includes two systems, one is an existing three-probe measurement system for measuring the ion density here; the other is composed of a metal ring probe, a filter circuit and a data acquisition system. When the current in the metal ring changes, an induced potential will be generated in the ring. By measuring and processing the induced potential, the current evolution in the ring (i.e., current density) is judged, and the ion energy in the ring is obtained by combining the current evolution in the ring and the ion density measurement results.

[0058] The present invention provides a novel ion energy measurement method in an electric thruster, which expands the ion energy measurement position from the thruster plume area to the inside of the thruster discharge chamber and can perform real-time monitoring, thereby promoting research on the energy coupling mechanism of high-power electric thrusters, optimizing thruster design, and promoting the rapid development of high-power electric thrusters.

[0059] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

[0060] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. An online measurement system for ion energy in high-power electric thrusters, It is characterized in that It includes an integrated probe located inside the discharge cavity of the electric thruster, and a data acquisition system located outside the discharge cavity of the electric thruster; The integrated probe includes a three-probe probe and a metal ring probe; the metal ring probe is an unclosed ring structure wound by metal wires, and the three-probe probe is located inside the metal ring probe and includes three metal wires arranged side by side; The data acquisition system acquires the induced potential generated inside the metal ring probe, and obtains the current density according to the induced potential. The data acquisition system simultaneously acquires the ion saturation current, positive bias potential and suspension potential of the three-probe probe, and obtains the ion density according to the ion saturation current, positive bias potential and suspension potential. The data acquisition system obtains the ion energy based on the current density and ion density; The data acquisition system is based on the ion saturation current I s + , positive bias potential V + and the floating potential V f , the ion density is obtained using the following formula: T e =(V + -V f ) / ln2 Where α is a constant related to the three-probe probe and plasma; T e is the timing signal of electron temperature; n e is the electron density timing signal, i.e., ion density; The ion energy is obtained according to the ion velocity v; The ion velocity v is determined by the current density J and the ion density n e , obtained by the following formula: J=n e ev Here, e is the charge of the electron.

2. According to claim 1, an online measurement system for ion energy in a high-power electric thruster, It is characterized in that Among the three metal wires arranged side by side in the three-probe probe, the head of the middle metal wire coincides with the center of the metal ring probe; The plane where the metal ring probe is located is perpendicular to the axis of the electric thruster discharge cavity.

3. The online measurement system for ion energy in a high-power electric thruster according to claim 1, It is characterized in that The integrated probe is fixed in the discharge cavity of the electric thruster in a pre-buried manner; The number of integrated probes is ≥3, and the multiple integrated probes are distributed along the axial direction of the electric thruster discharge cavity, and the distribution positions of the multiple integrated probes cover the discharge cavity; The three-probe probe is made of tungsten wire with a diameter of 0.3-0.8 mm; the metal ring probe is made of tungsten wire with a diameter of 0.1-0.3 mm.

4. The online measurement system for ion energy in a high-power electric thruster according to claim 3, It is characterized in that The metal ring probe is an open ring structure wound by metal wire, the two ends of the metal wire are the lead-out ends of the metal ring probe, and the tails of the three metal wires arranged side by side of the three-probe probe are the lead-out ends of the three-probe probe; ceramic tubes are arranged outside the lead-out ends of the metal ring probe and the three-probe probe, and the lead-out ends of the metal ring probe and the three-probe probe are connected to the data acquisition system after passing through the discharge cavity; the ceramic tubes outside the lead-out ends of the metal ring probe and the three-probe probe are sealed with the discharge cavity by sintering.

5. The online measurement system for ion energy in a high-power electric thruster according to claim 3, It is characterized in that Among the multiple integrated probes distributed axially in the discharge cavity of the electric thruster, the distance between the last integrated probe and the discharge cavity nozzle is 50 to 80 mm.

6. The online measurement system for ion energy in a high-power electric thruster according to claim 1, It is characterized in that It also includes filtering circuits and a three-probe control system; The filter circuit is an LC resonance circuit formed by connecting an inductor and an adjustable capacitor in parallel. The induced potential generated inside the metal ring probe is transmitted to the data acquisition system after passing through the filter circuit. The values ​​of the inductor and the adjustable capacitor of the filter circuit satisfy the following relationship: ω 2 =LC; Wherein, ω is the loading frequency of the RF power supply of the electric thruster, L is the inductance value, and C is the capacitance value of the adjustable capacitor; The three-probe control system is used to power the three-probe probe.

7. The online measurement system for ion energy in a high-power electric thruster according to claim 1, It is characterized in that The data acquisition system includes an acquisition card, an adapter board matching the acquisition card, and a PC; The induced potential generated inside the metal ring probe, as well as the electrical signals of the ion saturation current, positive bias potential and suspension potential of the three-probe probe are transmitted to the acquisition card through the adapter board. The acquisition card converts the electrical signals into digital signals and transmits the digital signals to the PC. The PC performs calculations based on the digital signals to obtain current density and ion density, and obtains ion energy based on the current density and ion density.

8. The online measurement system for ion energy in a high-power electric thruster according to claim 1, It is characterized in that The data acquisition system obtains the real-time evolution parameter of ion energy according to the real-time ion energy, and obtains the energy coupling efficiency of the electric thruster according to the real-time evolution parameter of ion energy.

9. A method for online measurement of ion energy in a high-power electric thruster. It is characterized in that The method is implemented by using the online measurement system for ion energy in a high-power electric thruster according to any one of claims 1 to 8, comprising the following steps: The data acquisition system acquires the induced potential generated inside the metal ring probe, and obtains the current density according to the induced potential. The data acquisition system simultaneously acquires the ion saturation current, positive bias potential and suspension potential of the three-probe probe, and obtains the ion density according to the ion saturation current, positive bias potential and suspension potential. The data acquisition system obtains the ion energy based on the current density and ion density.

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